Detonator to igniter adapter for initiating propellant mixes



C. H. BAGLEY Dec. 1, 1964 DETONATOR T0 IGNI TER ADAPTER FOR INITIATING PROPELLANT MIXES Filed April 5, 1962 INVENTOR. CHARLES H. BA GLEY ATTORNEYS United States Patent 3,159,103 DETONATQR T0 IGNITER ADAPTER FGR INITIATHQG PROPELLANT MIXES (Zharles H. Bagley, Sunnyvale, Calif., assignor, to Beckman & Whitley, Inc, San (Carlos, (Ialifi, a corporation of California Filed Apr. 5, 1962, Ser. No. 185,394 4 Claims; (Cl. 102-28) This invention relates to the initiation of burning of fuel in rocket motors and the like.

While detonators for high explosives are relatively sim-.

ple to construct, a detonator to initiate gas generators or propellant igniters as in rocket motors presents serious problems. When a secondary high explosive is used next to a propellant mix, it is possible for it to induce a shock of sufiicient magnitude to detonate the propellant mix rather than initiate burning thereof. Furthermore in existing detonating devices, it is common for the shock resulting from detonation of the secondary explosive to destroy its own container and, therefore, leave open or destroy the gas pressure seal of the propellant actuated device.

A common type of detonator employs a small quantity of primary explosive to detonate a secondary explosive which in turn affords the heat and pressure to ignite the propellant mix. The primary explosive is detonated by an electrical resistance wire embedded in it and energized by a suitable, low voltage current. This system has the disadvantages referred to above and the further disadvantage that the timing of detonation lack precision because static discharges may be sufficiently great to energize the i system to the point of detonation.

It is the object of the present invention to provide igniting means for rocket motors or the like employing socalled solid fuel or pyrotechnic mixes as a propellant which is capable of precisely timed dependable and safe operation and which is not self-destructive to the point of breaking the seal at the point where it is adapted to the body of the rocket for initiation of the burning of the fuel contained therein.

Further objects and advantages of the present invention and the manner in which'it is carried in topractice are made apparent in the following specification by reference to the accompanying drawing.

The drawing is a central sectional view through a detonator and adapter embodying the present invention.

It is well known that when a strong shock is sent through a solid such as a metal or plastic and the solid has a conical cavity so placed that the shock first impinges 0n the apex of the cavity, the surface material of the cone collapses toward the axis of the cone and produces a jet of high density particles of the solid traveling at an extremely high rate of speed. When this standard shape charge cone is formed in steel or other hard metal,

it is capable of producing a very strong piercing effect because of the high velocity of the metal particles forced into the jet by the pressure of the shock wave. This standard shape charge principleis employed inthe present invention for igniting a fuse of a pyrotechnic mixture which in turn initiates burning of an igniter mix in intimate contact with the fuel. In the presentinvention, the shape charge cone is embodied in a hard metal adapter of sufficient mass and proportion to absorb the shock waves .Another knowm principle employed in the present inset up for the purpose of creating the jet in the cone and permit them to disintegrate without destruction of the adapter itself;

vention is that of theexploding bridgewire heretofore employed for illuminating as well as detonating purposes opposite end of said body having a second cavity, a secand including a short length of fusible wire included in a circuit known as an exploding bridge wire circuit capable of directing a momentary high voltage current which may be timed with extreme precision to effect instant fusion or vaporization of the bridge wire accompanied by a very concentrated area of strong shock and extremely high temperature in its vicinity capable of positively detonating a secondary explosive.

The manner in which the two phenomena described above are embodied in an apparatus to provide a detonator to igniter adapter is shown in the accompanying drawing wherein the adapter is shown as a substantially cylindrical block of hardened steel or other equivalent metal at 10. At one end, this block is threaded as at 11 and has formed in it a central cavity for the reception of an igniter mix 12 so that when threaded into the body of a rocket or other fuel container, the igniter mix 12 can be in direct contact with the fuel to be burned. The opposite end' of the adapter has an internally threaded recess 13 for the reception of the threaded end of an exploding bridge Wire header 14. This header has a central bore partially closed at its upper end and containing a glass or other dielectric filler plug 16 through which wires 17 of a suitable circuit are led to an exploding bridge wire 18 which is embedded in a charge of a sensitive secondary explosive 19. The adapter 10 is provided with a small axial bore for the reception of a fuse 2% which leads from the cavity for igniter mix 12 to a point short of the cavity containing the secondary explosive 19 and terminates in a shape charge cone 21, the axis of which is in alignment with the fuse 20 and the center of the body of secondary explosive 19. j

In operation, energization of the exploding bridge wire circuit vaporizes the bridge wire and detonates the charge 19. The resulting shock set up in the body of the adapter 16 progresses downwardly toward the apex of the conical void 21, collapsing its walls and producing the high velocity high temperature jet which initiatesburning of the fuse 2t) and consequent burning of the igniter mix 12 and the fuel with which it is in contact.

The distance between the secondary explosive 19 which is detonated and the cone 21 is. relatively small compared to the length and diameter of the adapter 10 so that the force of the shock wave produced by detonation is suiiicient to collapse the cone and produce an effective jet. However, the mass of metal between the point of detonation and the igniter mix 12, and the rnass of metal between the point of detonation and the outer cylindrical surface of the adapter, is sutlicient to produce degradation of the original shock wave and its reflected components below the point where it is capable of detonating the igniter mix, or the fuel to be initiated, and below the point where the stresses set up within the metal are suflicient to effect its fracture and exposure to atmosphere of the high pressures which result from the burning of the fuel. It should be understood that the detonation which produces the shock wave that collapses the cone 21 for providing the igniting jet therein distorts but little of the metal between the cavity containing the explosive 19 and the cone so that the adapter remains in place as an effective seal after it has been used. 7

Thus the adapter of the present invention prevents accidetal detonation of the propellant providing adequate normal ignition thereof and positive gas pressure sealing after ignition.

I claim:

1. A detonator to igniter adapter comprising a substantially cylindrical solid metal body having a cavity in mixin intimate proximity to the propellant mix, the

ondary explosive in said second cavity, a fuse bore in the body containing a fuse extending from the igniter mix toward the secondary explosive, said bore terminating in a cone-shaped end spaced from the explosive mix cavity by solid metal of the body a distance which will enable detonation of the secondary explosive to collapse the cone and ignite the fuse, and said body being of a length and having sufficient metal surrounding the second cavity to effect attenuation of shock waves to prevent detonation of the propellant mix, to prevent detonation of the igniter mix and to prevent fracture of the body.

2. The combination of claim 1 with means for detonating the secondary explosive.

3. The combination of claim 1 with a bridge wire in the secondary explosive recess.

4. The combination of claim 1 in which the mass of the body between the secondary explosive recess and the shape charged cone is suificient to prevent fracture through the outer surface of the body.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A DETONATOR TO IGNITER ADAPTER COMPRISING A SUBSTANTIALLY CYLINDRICAL SOLID METAL BODY HAVING A CAVITY IN ONE END, AN IGNITER MIX IN SAID CAVITY, MEANS FOR SEALING SAID END TO A CONTAINER FOR PROPELLANT MIX WITH THE IGNITER MIX IN INTIMATE PROXIMITY TO THE PROPELLANT MIX, THE OPPOSITE END OF SAID BODY HAVING A SECOND CAVITY, A SECONDARY EXPLOSIVE IN SAID SECOND CAVITY, A FUSE BORE IN THE BODY CONTAINING A FUSE EXTENDING FROM THE IGNITER MIX TOWARD THE SECONDARY EXPLOSIVE, SAID BORE TERMINATING IN A CONE-SHAPED END SPACED FROM THE EXPLOSIVE MIX CAVITY BY A SOLID METAL OF THE BODY A DISTANCE WHICH WILL ENABLE DETONATION OF THE SECONDARY EXPLOSIVE TO COLLAPSE THE CONE AND IGNITE THE FUSE, AND SAID BODY BEING OF A LENGTH AND HAVING SUFFICIENT METAL SURROUNDING THE SECOND CAVITY TO EFFECT ATTENUATION OF SHOCK WAVES TO PREVENT DETONATION OF THE PROPELLANT MIX, TO PREVENT DETONATION OF THE IGNITER MIX AND TO PREVENT FRACTURE OF THE BODY. 